Processes for the manufacture of parts which basically comprise a first stage of laying-up sheets by means of ATL “Automatic Tape Lay-Up” and a second stage of curing in an autoclave are well-known in the aviation industry.
During the lay-up stage layers of composite material such as a prepreg, which is a storable mixture of fibre reinforcement and polymer matrix, are placed in a mould/tool of suitable shape.
This material may be in various forms and in particular in the form of a sheet. In the case of thermo-hardening matrices the resin is generally partly cured or brought to a controlled viscosity, known as the B-stage, by another process.
Sheets of composite material are not located randomly but are positioned in each zone in a number and having an orientation of their fibre reinforcement, typically carbon fibre, which are determined according to the nature and magnitude of the forces which the part must withstand in each zone. ATL (“Automatic Tape Lay-Up”) machines are generally used for this.
Automatic tape lay-up machines are very efficient for manufacturing flat or substantially flat lay-ups given that the permissible gradients for such machines are small.
Nevertheless there are aircraft structures which include wedges which, although it would be desirable from the design point of view that they should have gradients greater than those permissible for ATL machines, are finally designed with smaller gradients in order to comply with the manufacturing constraints of these machines. This gives rise to various disadvantages which this invention is intended to overcome.